Abstract:

This paper presents an analytical theoretical model for air-boosted vacuum preloading, focusing on the influence of air injection on soil consolidation. A simplified force model based on the equivalence of air-boosted pressure is proposed, and a new parameter called the “horizontal permeability coefficient increase parameter h” is introduced to account for changes in soil permeability due to gas injection. Based on Barron equal vertical strain assumption and linear Darcy’s law, the governing equation and consolidation analytical solution for air-boosted vacuum preloading are derived, considering factors such as radial and vertical seepage, prefabricated vertical drain smear effect, well resistance, and surcharge. Additionally, the theoretical formula for the equivalent air-boosted pressure p(t) is derived using elastic mechanics methods. Specific analytical solutions are provided for two cases: instantaneous air-boosted and linear air-boosted. An engineering case study is used to verify the rationality of the analytical solution and the mechanical equivalence method. Through the analysis of consolidation behavior, the following conclusions are drawn: the air injection boosting method increases the negative pore water pressure in the soil, facilitating faster drainage and consolidation; the “η ” parameter significantly affects the consolidation rate, and considering changes in the horizontal permeability coefficient during gas injection improves the accuracy of the analysis model; well resistance slows down the consolidation rate, and while pore pressure can dissipate completely during radial and vertical seepage, it may not dissipate completely during radial seepage alone.

Key words: air-boosted vacuum preloading, equal strain condition, consolidation theory, analytical solution